Current Trends in the Surgical Treatment of Fibular Fractures: A National Database Study of Intramedullary vs. Plate Fixation Practice Patterns, Complications, and Cost

Existing primary evidence comparing fibular intramedullary fixation (IMF) with traditional plate fixation (PF) for the treatment of distal fibular fractures remains limited by modest sample sizes. Using a large national database, this study aims to compare use rates, fracture patterns, patient characteristics, time to surgery, complication rates, and cost between fibular IMF and PF within the United States. Adults treated with fibular IMF or PF between October 2015 and October 2021 were identified within the PearlDiver Database. The ratio of IMF-treated to PF-treated patients was tracked temporally to compare use rates. Fracture patterns were determined using fracture diagnoses within one-month preceding surgery. Further comparisons of IMF- and PF-treated groups only included patients with at least 12 months of follow-up, and patients with upper tibia or tibia shaft fractures were excluded. An analysis of cohorts matched at a 1 : 4 (IMF: PF) ratio to control for risk factors was performed to compare time to surgery, complication rates (infection, nonunion, malunion, revision, hardware removal, pulmonary embolism, and deep vein thrombosis), and cost. 39329 patients (2294 IMF and 37035 PF) were identified. IMF use trended upwards relative to PF use over time. Tibia and fibula shaft fractures were the most common injuries in IMF patients versus bimalleolar and trimalleolar fractures in PF patients. A higher proportion of IMF patients had open fractures. IMF patients were younger, with higher mean ECI, fewer female patients, and higher rates of CKD. Percutaneous approaches were more common among IMF patients. There were no significant differences in time to surgery or complication rates. IMF was less costly. The popularity of IMF trended upwards across the study period. IMF was used more commonly in injuries involving higher energy trauma and soft tissue disruption. Overall, IMF patients were younger with more comorbidities. When used in similar populations, IMF appears to be a cost-effective alternative to PF.


Introduction
Globally, ankle fractures are among the most common fractures and are also among the most burdensome in terms of years lived with disability [1][2][3].Te frequency of these fractures, particularly those resulting from low-energy trauma in older adults, is on the rise [4][5][6][7][8][9][10].Te vast majority of ankle fractures involve the distal fbula [4,7,[11][12][13][14] and often occur in conjunction with other fractures [15].Surgery is indicated for distal fbula fractures that are considered unstable [15]; historically, the most common operative approach in these cases has been open reduction with plate and screw internal fxation [16,17].As ankle fractures become more common in older adults and complication rates from standard fxation methods create challenges in higher-risk populations (e.g., diabetics, tobacco-users, and older adults) [18][19][20][21][22], continued investigation of treatment strategies that aim to reduce complications and improve outcomes is warranted.
Many studies have already reported promising results from the use of fbular intramedullary devices.A 1986 study on the Inyo Nail, one of the earliest fbular intramedullary nails studied in the literature, reported faster recovery times and better rates of complications, and morbidity for those treated with nail fxation compared to those treated with plate fxation [34].More recent studies comparing intramedullary fxation to plate fxation of the fbula have also reported benefts in the use of intramedullary devices, including fewer complications, better functional outcomes, faster recovery times, and lower costs [24,[35][36][37][38].However, the results reported within the current body of literature are not in complete agreement, and there remains a need for further research to reach consensus on the optimal implant for distal fbular fractures.Furthermore, little is known about the current utilization rates of intramedullary fbular fxation.Using a nation-wide United States administrative claims database, we aim to compare use rate trends, fracture patterns, patient characteristics, complication rates, time to surgery, and cost between plate fxation (PF) and intramedullary fxation (IMF) of distal fbular fractures.We hypothesize that (1) fbular IMF use is increasing relative to PF use in the United States, that (2) fbular IMF is being used more often in patients with greater comorbidities and higher severity injuries compared to PF, and that (3) fbular IMF allows for similar or lower times to surgery, complication rates, and overall cost compared to PF.

Study Design and Database.
A retrospective cohort study was conducted using the PearlDiver Mariner Database (PearlDiver Technologies, Colorado Springs, Colorado, USA), a national insurance claims database that contains deidentifed records from nearly 157 million patients.Patients within the database were selected and fltered for this study using International Classifcation of Diseases, 10th Revision, Clinical Modifcation and Procedural Coding System (ICD-10-CM and ICD-10-PCS) codes and Current Procedural Terminology (CPT) codes.It is important to note that, while the Mariner Database allows longitudinal retrospective study of complication rates through the tracking of documented billing codes across multiple encounters, it is not possible to track functional or patient reported-outcomes using the database, as these are not typically captured using these codes.
Te study population included adult patients (age ≥18 years) treated with plate or intramedullary fxation of the distal fbula between October 2015 and October 2021.

Data Collection.
All adult patients treated with plate or intramedullary internal fxation of the fbula were identifed using ICD-10-PCS codes for internal fxation (i.e., plate fxation) or intramedullary internal fxation of the fbula (Supplemental Table 1).

Trends in Use Rates and Associated Fracture Patterns.
To determine diferences in the types of fractures associated with fbular intramedullary and plate fxation, patients with lower leg or ankle fractures that were treated with internal fxation within one month following diagnosis were selected using ICD-10-CM codes for fracture of the lower leg, ankle, tibia, or fbula (Supplemental Table 2).A trend analysis over this period was performed to compare changes in monthly patients treated between the two fxation types.

Comparison of Patient Characteristics.
To determine diferences in patient characteristics, 90-day total costs, complication rates, and time to surgery between fxation types, only patients with documented fbula fractures who could be tracked for at least 12 months following surgery were included for analysis, and any patients with concomitant upper tibia or tibia shaft fractures were excluded to ensure that only patients with isolated lower leg and ankle injuries were included (Figure 1).Both ankle and fbula shaft fractures were included to capture all distal fbula fractures treated with internal fxation.Data gathered on patient characteristics included age, gender, US region, operative approach (open or percutaneous), diabetes mellitus (DM), chronic kidney disease (CKD), obesity, tobacco use, osteoporosis, and Elixhauser Comorbidity Index (ECI).ECI is a measure of comorbidity burden, designed to predict risks of in-hospital mortality and 30-day readmission [39].

Analysis of Postoperative Complications and Cost Using Matched Cohorts.
Patients with open fractures of the lower leg or ankle were additionally excluded in the analysis of cost, time to surgery, and complication rates to optimize the comparability of groups and ensure that only patients with closed distal fbular fractures were being compared between fxation types.Patients from each treatment group were then sampled randomly and matched at a 1 : 4 (IMF: PF) ratio (Figure 1).Te matching process was performed using an exact match methodology to control for the following risk factors: age, gender, DM, obesity, tobacco use, CKD, and associated high-energy fracture (i.e., pilon, lower tibia, and trimalleolar fractures).According to exact match methodology, each PF-treated patient was matched to four IMFtreated patients that fulflled all the exact same matching criteria.Time to surgery was measured in days spanning from the date of the initial diagnosis to the date of index surgery.Complications of interest included infection, nonunion, malunion, revision, hardware removal, pulmonary embolism (PE), and deep vein thrombosis (DVT).Infection, PE, and DVT were assessed within the 90 days 2 Advances in Orthopedics following surgery; revision and hardware removal within one year following surgery; and nonunion and malunion between fve weeks and one year following surgery.Cases of nonunion or malunion were only counted if patients additionally had a record of radiologic imaging of the lower leg or ankle that preceded any fbula nonunion or malunion diagnosis within the 5-week to 12-month window.Any cases of hardware removal were only counted as such if they were not associated with a revision procedure.Cost analysis was assessed by totaling all costs across a 90-day period starting from the date of surgery.

Statistical Analysis.
Statistical analyses were aimed at comparing IMF to PF, as PF is the standard, most widely used fxation type for distal fbular fractures.To analyze diferences between the two fxation types, Pearson's chisquared test was used for comparison of categorical variables and Student's T-test for comparison of continuous variables.Linear least-squares regression was performed to generate a trendline for the trend analysis.
All statistical methods, including the matching process, were conducted using R Statistical Software (v4.1.2;R Core Team 2021), and pvalues less than 0.05 were considered statistically signifcant.

Trends in Use
Rates and Associated Fracture Patterns.39,329 patients treated with intramedullary fxation (IMF) or plate fxation (PF) of the fbula were identifed: 2,294 received IMF and 37,035 received PF (Figure 1).Te monthly ratio of patients receiving IMF compared to patients receiving PF trended signifcantly upwards across the study period, demonstrating a steady increase in IMF use relative to PF use (Figure 2).Higher proportions of open fractures of the lower leg or ankle were observed among IMF-treated patients than PF-treated patients (28.6% [n � 657] vs. 15.9%[n � 5,907], p < 0.001).Te most prevalent fracture diagnoses among IMF-treated patients were fbula shaft (64.8% [n � 1,487]) and associated tibia shaft (67.4% [n � 1,547]) fractures, while the most prevalent fracture diagnoses among PF-treated patients were bimalleolar (38.3% [n � 14,173]) and trimalleolar fractures (38.4% [n � 14,233]).Te proportions of these respective fracture diagnoses, as well as many other associated fracture diagnoses, signifcantly difered among IMF-treated and PFtreated patients (ps < 0.001) (Table 1).Higher percentages of diabetes, complicated diabetes, tobacco use, obesity, and osteoporosis were also observed in IMF-treated patients; however, these diferences were not signifcant (Table 2).Additionally, a higher proportion of percutaneous approaches were performed in patients receiving IMF compared to those receiving PF (28.9% [n � 181] vs. 1.6% [n � 482], p < 0.001) (Figure 3).Te only signifcant US regional diferences among IMF and PF groups was a signifcantly higher proportion of IMF patients being from the South compared to PF patients (Figure 4).

Postoperative Complications and Cost between Matched
Cohorts.1,570 patients were included in the 1 : 4 (IMFtreated:PF-treated) matched analysis: 316 patients received IMF and 1,254 received PF for closed lower leg fractures involving the distal fbula (Figure 1).No signifcant diferences in relevant patient characteristics were observed between these matched cohorts (Supplemental Table 5).In our analysis of this study group, no signifcant diferences were observed in proportions of postoperative complications of interest, including infection, nonunion, malunion, revision, hardware removal, pulmonary embolism, and deep vein thrombosis (Table 3).Moreover, no signifcant diferences were observed in mean days to surgery (Table 3).However, mean total 90-day cost (in USD) of IMF-treated patients was about $2,600 lower compared to PF-treated patients ($6585.58± $10908.50 vs. $9217.24± $17772.32,p � 0.012) (Table 3).

. Discussion
Te optimal construct and fxation technique for injuries involving the fbula continues to evolve as surgical techniques and technology improve.Fibular nail technology potentially ofers advantages over conventional plate and screw fxation, but this technology remains nascent with only small series reporting outcomes and usage.Our study showed that the rates of patients receiving IMF compared to patients receiving PF have trended upwards.Overall, combined tibia and fbula shaft, lower tibial, and open fractures were more common among IMF-treated patients, while bimalleolar and trimalleolar fractures were more common among PF-treated patients.Intramedullary fxation was also more commonly utilized in those with a greater burden of comorbidities.Te high percentage of open and tibia shaft fractures associated with IMF use suggests that IMF is more likely to be used in complex, higher energy injuries, where injury to the fbula may not be the dominant feature of the trauma sustained or when soft tissue concerns necessitate a less invasive approach.Alternatively, it may also be that surgeons treating Weber-C or other high distal fbula fractures (i.e., fbula shaft) may fnd or believe that an intramedullary implant provides a more stable construct than plating.It is interesting to note that fbular IMF was most used not for isolated ankle fractures, but rather in situations when there was a higher energy injury to the limb, especially in association with tibial shaft fractures.Importantly, despite the diferent clinical use cases that appear to exist between these two fxation types, the current study does not clearly isolate trends in the treatment of ankle fractures, but rather more broadly identifes how intramedullary fxation of fbula fractures is applied by orthopedic surgeons.
To our knowledge, this study is the frst to examine trends in the use rates of fbular intramedullary fxation within the United States.Te increasing popularity observed may be explained by the advent of novel intramedullary nail devices for the fbula.Te growing amount of literature supporting the purported benefts of these devices, most specifcally, fbula-specifc intramedullary nails, may be resulting in their increased use as an innovative treatment strategy in high-risk patients, including those with complex injuries [40,41].Analogous to our study, which focuses on United States trends, a 2021 study that analyzed trends in the operative treatment strategies for distal fbula fractures in Germany found that the rate of intramedullary nail use for distal fbular fxation increased from 0.1% to 1.0% between 2005 and 2019 [42].
Te present study is also the frst to our knowledge to comprehensively examine the fracture patterns IMF is associated with treating.Stake et al. investigated the use of fbular intramedullary nails in a hospital where intramedullary nails were primarily indicated for patients with compromised soft tissue, including those with open fractures or preoperative wounds or blisters at the surgical site [43].In concordance with Stake et al. [43], our study found that IMF was more highly associated with treating open fractures of the lower leg and ankle when compared to PF.In a prospective study of patients with fbular fractures associated with distal tibia and tibia shaft fractures, Stewart et al. stated that the indications for use of a distally locked fbular intramedullary nail include complex injuries or compromised soft tissue [44].Like the injuries described in that study [44], our study found that complex, high-energy fracture patterns were highly associated with IMF use.Compared to PF-treated patients, IMF-treated patients in our study were much more likely to have associated distal tibia and tibia shaft fractures, the same patterns studied by Stewart et al. [44].Furthermore, Stewart et al. concluded that using a fbular nail to treat fbula shaft fractures associated with pilon or tibia shaft fractures allowed for minimally invasive approaches and low complication rates while also providing stable fxation [44].Along with tibia shaft fractures, fbula shaft fractures were seen at a markedly high frequency among IMF-treated patients in our study, and a less invasive percutaneous approach was also more common among IMF-treated patients in our study.Tis suggests that the motivations for using an intramedullary nail, as described by Stewart et al. [44], may be common among surgeons utilizing fbular IMF for this complex injury pattern.Of note, the percentage of IMF-treated patients treated via a less invasive percutaneous approach in our Advances in Orthopedics study (28.9%) is similar to the 30% of fbular intramedullary nail patients treated with a percutaneous reduction in a series of 10 patients reported by Tonks [45].
Te existing literature on the applications of fbular IMF has revolved around its use in high-risk patients, including older adults [37,[46][47][48][49] as well as those with multiple
In agreement with the current literature, our study found

Advances in Orthopedics
higher percentages of all comorbidities and an overall signifcantly higher mean Elixhauser Comorbidity Index among IMF-treated patients compared to patients receiving PF for distal fbular fractures.However, the average ECI for both groups were relatively low, and the statistically signifcant diference of 0.49 between average ECI scores (i.e., on average, an IMF patient had 0.49 more comorbidities than a PF patient) may not be clinically signifcant.Our study also showed that patients receiving IMF for distal fbular fractures were signifcantly younger on average than patients receiving PF even after considering a narrower subset of associated fracture patterns (i.e., excluding concomitant tibia shaft and upper tibia fractures).Since younger patients are more likely to have high-energy trauma compared to older patients who are more likely to sufer from low-energy fragility injury [4,6,55] the comparatively younger age of IMF-treated patients to PF-treated patients may refect our fndings that IMF-treated injuries were more complex, with a higher degree of wound disruption and anatomic associations indicative of higher energy trauma.Despite the IMF group being younger on average than the PF group, most of both cohorts still fell into the ages 60 and over age groups rather than younger age deciles.Patients constituting older age groups are expected to have higher comorbidity burdens, and since comorbidities were assessed between IMF-and PF-treated patients via bivariate analyses (i.e., unadjusted for age), the relatively lower age of IMFtreated patients compared to PF-treated patients may have even defated the levels comorbidities across the IMF-treated cohort.Hence, it may be the case that older patients receiving IMF compared to older patients receiving PF had even higher average comorbidity burdens than were apparent from our data, which would align with indications for IMF in elderly patients with impaired wound healing [37,[46][47][48][49].
While a higher degree of comorbidities, including diabetes, has been discussed as a potential indication for IMF in prior literature [48,50,51], CKD is not well-discussed as an indication for fbular IMF; yet, CKD was the only comorbidity found at signifcantly higher proportions in IMF-treated patients compared to PF-treated patients in our study.CKD is a known risk factor for poor bone quality, both thrombotic and bleeding complications, and impaired wound healing [56][57][58] and patients with renal disease are often highly comorbid [58], which may simultaneously explain both the higher proportions of CKD and higher mean Elixhauser Comorbidity Index found among IMFtreated patients.Tus, the higher proportion of CKD found among IMF patients in our study may be further evidence that surgeons are turning to IMF as a strategy to minimize the burden of postoperative wound healing and risk of wound-related complications in high-risk patients.
To our knowledge, this is the frst study to use matched cohorts to systematically control for diferences in risk factors, including comorbidities and severity of injury, when comparing fbular IMF and PF.Te use of matching is particularly important given that our fndings showed differences in both patient characteristics and fracture diagnoses treated between the IMF and PF cohorts.Given that our fndings suggest that there is a preference for choosing IMF over PF in patients with greater comorbidities and injuries involving greater wound disruption and higher energy fracture patterns, it is crucial that we controlled and matched for these factors during our analysis to minimize the possibility that any diferences observed are attributable primarily to confounding patient-and fracture-related factors rather than the fxation type chosen.Despite the benefts of fbular IMF reported in the current literature, our study did not fnd IMF to be associated with signifcant diferences in time to surgery or outcomes except for lower 90-day total costs after adjusting for these risk factors.Overall, we found low percentages of malunion and nonunion in both groups, which agrees with prior and more recent systematic reviews/meta-analyses; however, there were no diferences in percentages between groups [27,38,59].Additionally, in accordance with existing evidence, there were no signifcant diferences in PE, DVT, implant removal, or revision between groups [28,37,60,61].We found that diferences in postoperative rates of infection were not statistically signifcant between cohorts, which disagree with recent meta-analyses showing signifcantly decreased postoperative infection rates and wound-related complications in IMF-treated patients [28,62].Furthermore, higher rates of infection among our matched cohorts than that reported in relevant meta-analyses [27,28,62] may be explained by our inclusion of superfcial and deep infections in the same analysis as opposed to separate analyses [27], higher average age [63], and prevalence of diabetes of almost 50% [51] among our matched cohorts.
While IMF implants encompass a wide range of devices from simple k-wires and rods to more sophisticated nail designs that could not be controlled for in our cost analysis, our fndings align with those of White et al., which did account for upfront implant costs and still showed a decreased overall average cost of healthcare delivery per patient with fbular IMF compared to PF for ankle fracture fxation [24].Reasons for improved cost-efectiveness of fbular IMF compared to PF may be due to the benefts of lower reoperation rates [28], decreased need for follow-up hardware removal [27], or decreased operative time [24], though these points are debated in the literature [24,27,28,64] and were not shown by our study.Given that we did not account for regional diferences with our matching process and that a signifcantly higher proportion of IMF patients were from the South compared to PF patients, another possibility for the diference in cost observed could be due to regional variations in reimbursement associated with IMF and PF.However, because regional make-up was not included within the matching criteria, our matched analysis is not designed to clarify this possibility.Lastly, we also observed a wide range in costs in both groups, so interpretation of these fndings should take that into consideration as well.

4.1.
Limitations.An inherent limitation of this study is its reliance on the billing codes available for identifying and properly fltering patients within the database [65,66].Most limiting was the lack of descriptive billing codes available for identifying intramedullary fbular fxation.While the CPT code 27759 is available for identifying tibia shaft fractures treated with intramedullary implants, there is no such CPT code for the use of intramedullary implants for fxation of fbular fractures.Tis study instead relied on ICD-10 PCS codes for identifying intramedullary fxation of fbular fractures, which limited our sample to an inpatient sample, prevented us from identifying patients treated prior to October 2015, and may have failed to capture patients whose treatment was documented using only CPT codes.An important consequence of this limitation is that this study may be selecting for patients requiring hospital admission associated with their surgery, which may skew the study sample towards those requiring higher-level care (i.e., sicker or more severely injured patients).To avoid introducing possible bias into any comparative analyses due to this limitation, plate fxation patients were also only identifed using ICD-10 PCS codes.Furthermore, the codes available do not distinguish between the various devices that fall under the umbrella of intramedullary fxation devices [65,66], limiting our ability to interpret our fndings more comprehensively.Billing codes are also limited in their level of descriptiveness and clinical relevance.Because much of the recent literature has focused on the use of IMF in treating ankle fractures of the distal fbula, the high percentage of fractures documented as fbula shaft fractures observed in the IMF-treated group was unexpected.Tis was likely related to the presence of concomitant tibial shaft fractures in these patients.Without access to direct patient data (e.g., patient charts), however, it is not possible to clarify this fnding further.It is also important to emphasize that, while longitudinal tracking across extended time-periods is possible using PearlDiver, functional and patient reportedoutcomes are not tracked in PearlDiver, as these types of outcome measures are not captured using billing codes.Lack of access to functional and patient reported outcome measures, ordinarily reported as means and ranges, also limits this study's capacity to report on score ranges for important outcome measures, which might otherwise shed light on the consistency of results associated with IMF use compared to PF use.Because of this limitation, this study was limited to reporting primarily rates and percentages (i.e., complication rates).Additionally, given that fbular IMF is much less commonly utilized than PF, surgeon experience is an important factor to consider when studying outcomes, but the database does not provide this information.
Lastly, while we employed a strategic matching process to control for diferent patient characteristics and the degree of energy associated with a fracture pattern, the overall number of cases made it infeasible to fully include the wide array of fracture diagnoses as separate matching criteria.Furthermore, the inclusion of additional fracture classifcation analysis (e.g., Weber or Hansen classifcations) is not only not possible with the limited data provided by the PearlDiver database, it is also not without additional inherent bias given the inter-rater variability and reliability concerns of these classifcations.Our matching criteria instead were carefully selected to include the most relevant patient characteristics based on existing literature (i.e., age, gender, DM, obesity, tobacco use, and CKD) and a high-vs.low-energy fracture criterion to account for the difering fracture types found between IMF-and PF-treated patients in our study.Te number of IMF cases also precludes meaningful sub-analysis of exclusively higherrisk cases (i.e., patients with comorbidities or specifc fracture patterns).Finally, the very small percentage of percutaneous approaches among PF patients precludes the possibility of including operative approach (open vs. percutaneous PF) as a matching criteria, as there are insufcient percutaneously treated PF patients to match to percutaneously treated IMF patients with our specifed matching process.

Conclusions
Tis study suggests that the use of fbular IMF is steadily rising.Moreover, we found that IMF and PF were associated with treating diferent injury patterns.IMF use was more often associated with treating higher energy injuries, those with soft tissue disruption, fbular injuries associated with tibial shaft fractures, and medically complex patients with comorbidities that may impair wound healing.Cost data suggests that fbular IMF appears to be a cheaper alternative to PF that yields comparable outcomes for treatment of Advances in Orthopedics distal fbular fractures; however, additional cost and efcacy studies are required.

Figure 3 :
Figure 3: Operative approach (open vs. percutaneous) by fxation type.IMF and PF groups difered signifcantly with respect to operative approach, with IMF-treated patients more commonly undergoing fxation via percutaneous approaches compared to PF patients, and PF patients more commonly undergoing fxation via open approaches compared to IMF patients ( * p < 0.001).

Figure 4 :
Figure 4: United States regions of IMF and PF patients by fxation type.A signifcantly higher proportion of IMF patients were treated in the South compared to PF patients (47.5% of IMF patients vs. 41.8% of PF patients, * p � 0.004).No other signifcant diferences with respect to US regions among patients were observed.

Table 3 :
Rates of postoperative complications, time to surgery, and cost by fxation method.